UNIVERSITY  OF   CALIFORNIA. 

AGRICULTURAL  EXPERIMENT  STATION. 

BERKELEY,  CAL. 

E.  W.  HILGARD,  Director.  BULLETIN  No.  104. 


INVESTIGATIONS  OF  CALIFORNIA  OLIVES 
AND  OLIVE  OILS. 


APRIL,  1894. 


INVESTIGATIONS  OF  CALIFORNIA  OLIVES  AND  OLIVE  OILS. 

By  A.  P.  Hayne,  Ph.B.,  Assistant  in  charge  of  Viticulture  and  Olive  Culture. 


The  work  done  in  the  Olive  Laboratory  of  the  Agricultural  Experi- 
ment Station  of  the  University  of  California  during  the  season  of 
1893-94  was  on  a  larger  scale  than  heretofore.  The  University  Culture 
Stations  were  unable,  owing  to  the  youth  of  the  trees,  to  furnish  olives 
for  experiment;  but  public-spirited  growers  from  many  parts  of  the 
State  donated  a  sufficient  quantity  to  enable  the  Central  Station  at 
Berkeley  to  make  some  valuable  experiments  in  oil  making  and  analy- 
sis. Sixty-seven  samples  of  olives  were  received  from  ten  of  the  leading 
olive-growing  regions  of  the  State.  Ten  of  these  samples  were  each 
large  enough  to  be  made  into  oil.  The  entire  sixty-seven  were  analyzed 
by  George  E.  Colby,  Instructor  and  Chemist  in  the  Viticultural  Labora- 
tory of  the  Station. 

Before  reporting  upon  the  experiments,  it  is  desirable  to  give  some 
general  data  in  regard  to  the  various  points  involved. 

MATURITY    OF   THE    OLIVE. 

It  seems  to  be  a  common  belief  in  California  that  the  proper  state  of 
maturity  of  olives  is  when  they  have  reached  jet-blackness;  also,  that 
it  makes  little  difference  how  long  they  remain  on  the  tree,  or  in  storage 
after  being  picked.  This  is  an  error,  not  only  as  regards  the  making  of 
oil,  but  the  pickling  of  the  fruit  also.  The  quantity  of  oil  in  the  flesh 
is  the  same  at  the  time  of  redness  as  it  is  a  month  after  the  jet-black 
color  has  been  reached,  so  there  is  nothing  to  be  gained  in  quantity  by 
delaying  the  harvest.  What  is  of  more  importance  is  that  the  quality 
of  the  oil  in  the  olives  deteriorates  the  longer  they  are  allowed  to  remain  on 
the  tree  after  proper  maturity  (redness)  has  been  reached;  for  the  olein, 
which  gives  true  quality  to  olive  oil,  diminishes;  and  the  stearin,  or 
solid  "  greasy"  substance,  increases.  On  the  European  market  "  greasy" 
oils  bring  lower  prices  than  oils  without  this  "  greasy  taste." 

While  it  is  true  that  some  varieties  naturally  have  more  stearin  than 
others,  yet  it  is  equally  true  that  this  "  greasiness  "  is  greatly  lessened 
by  early  harvesting.  In  two  lots  of  "  Rubras  "  received  at  the  Univer- 
sity this  year,  one  of  a  wine-red  color,  and  the  other  jet  black,  this  differ- 
ence was  noted  at  once,  even  by  persons  not  accustomed  to  sampling  oil. 
But  aside  from  this  "  greasy  "  or  "  lardy  "  taste,  oil  made  from  over-ripe 
olives  is  more  apt  to  "  cloud,"  and  to  deposit  a  granular  sediment  in  the 
bottles,  than  in  the  case  of  oil  made  from  what  are  considered  "  under- 
ripe" olives.  Should  the  temperature  fall  to  45°,  the  oil  of  the  over- 
ripe olive  will  solidify,  while  that  of  the  other  will  remain  clear  and 
brilliant  till  the  temperature  falls  8°  or  10°  lower.  As  a  rule  the  pur- 
chaser will  prefer  a  clear,  brilliant  oil  to  a  solid  one. 


—    3    — 

Right  here  it  would  be  well  to  note  that  a  popular  idea  seems  to  be 
that  if  an  oil  solidifies  even  at  the  freezing  point  of  water,  it  is  adulter- 
ated, while  an  oil  remaining  clear  at  the  same  temperature  is  pure. 
This  is  a  misconception;  for  both  pure  olive  oil,  and  the  oils  usually  used 
for  adulteration,  solidify  at  about  the  same  temperature;  the  difference 
generally  being  that  partially  clarified  oil,  or  oil  made  from  over-ripe 
olives,  is  the  first  to  solidify  or  "  freeze."  It  was  found  that  olives 
picked  in  an  "under-ripe"  condition  gave,  almost  without  exception, 
an  oil  of  a  darker  color;  the  jet-black  olives  gave  oils  much  lighter  or 
yellower  in  color;  while  the  red  olives  almost  invariably  gave  that 
beautiful  olive-green  tint  that  characterizes  the  highest  grades  of  oil, 
due  allowance  being  made  for  variety  characteristics. 

Another  striking  point  brought  out  by  the  experimental  work  in  the 
oil-room  was  that  the  same  variety  of  olive  grown  in  different  localities 
yielded  oils  differing  very  strikingly  in  quality.  Thus  several  lots  of 
the  so-called  Redding  Picholine  were  received,  some  of  which  were 
grown  in  deep  rich  bottom  land,  and  others  either  on  gravelly  hillsides 
or  on  higher,  well-drained,  light  soils.  In  every  case  the  oil  from  the 
hillside  olive  was  superior  to  that  from  the  low  lands.  Oil  from  the 
rich  soils  was  always  harder  to  clarify,  and  prone  to  cloud  up  and 
solidify  much  sooner  than  that  from  poorer  soils. 

The  Redding  Picholine  yields  at  best  an  oil  of  doubtful  quality,  but 
the  difference  in  its  oil,  due  to  different  classes  of  soil,  was  most  strik- 
ingly illustrated.  Not  only  was  this  noted  in  the  case  of  the  Redding 
Picholine,  but  also  with  Rubra,  Oblonga,  and  varieties  that  give  high 
grades  of  oil. 

FROZEN    OLIVES. 

There  are  few  parts  of  the  olive-growing  regions  of  the  world  where 
an  exceptional  season  or  an  early  frost  does  not  sometimes  surprise  the 
grower  before  the  harvest  is  completed.  The  fruit  of  the  olive  is  much 
more  sensitive  to  the  effects  of  cold  than  the  tree  itself.  Hence,  in  locali- 
ties thus  subject  to  early  frosts,  care  should  be  taken  to  plant  only  those 
varieties  that  mature  early,  for  once  an  olive  has  been  frost-bitten,  it  is 
next  to  impossible  to  make  a  salable  oil  out  of  it,  and  it  is  quite  impos- 
sible to  make  a  pickle  that  can  be  eaten.  The  water  in  the  juice  of  the 
olive  freezes,  and  in  so  doing  expands,  tearing  the  tissue  of  the  flesh. 
This  of  itself,  of  course,  would  not  injure  the  quantity  or  quality  of  the 
oil  in  any  way,  but  unless  the  frost-bitten  berry  is  at  once  crushed  and 
the  oil  expressed,  the  broken  tissue  decomposes  and  imparts  to  the  oil  a 
most  disagreeable  taste  and  odor,  rendering  it  unfit  for  the  table. 

Among  the  samples  of  olives  received  at  the  Station  this  year  were 
several  that  had  been  frost-bitten,  either  before  picking  or  while  awaiting 
shipment.  These  were  separately  made  into  oil  as  soon  as  possible.  It 
was  found  that  a  delay  of  three  days  from  the  time  the  olives  were 
frozen  to  the  time  of  crushing  and  pressing,  was  fatal.  The  oil  was,  to 
the  eye,  as  clear,  and  to  all  external  appearances,  as  good  as  that  made 
from  unfrozen  olives,  but  the  taste  was  such  as  to  render  it  unfit  for  use. 
The  odor  was  very  disagreeable  and  very  pronounced,  and  those  who 
tasted  the  oil  pronounced  it  "  made  from  fermented  olives." 

When  we  consider  that  a  delay  of  three  days  in  crushing  caused  this, 
we  can  at  once  realize  the  importance  of  early  harvesting,  and  therefore, 
of  the  selection  of  early  maturing  varieties  to  escape  frost,  for  on  a  large 


—    4    — 

scale  it  would  practically  be  impossible  to  express  the  oil  any  sooner 
than  three  days. 

This  fact  accentuates  the  importance  also,  of  picking  the  fruit  as  soon 
as  it  reaches  true  maturity,  instead  of  leaving  it  on  the  trees  any  longer 
than  is  absolutely  necessary. 

From  the  University  Experiment  Stations  it  was  learned  that  the 
Nevadillo  Blanco  was  the  first  to  be  frost-bitten,  the  Nigerina  second, 
and  the  Pendulina  third.  This  being  an  exceptionally  severe  season,  it 
was  found  that  at  the  four  Stations  where  there  were  olive  trees  in  bear- 
ing, all  of  the  varieties  were  frozen  before  the  first  of  January. 

OIL-MAKING    MACHINERY. 

In  1892  the  University  imported  from  Saragossa,  Spain,  two  newly- 
invented  machines,  said  to  be  of  great  importance  to  the  olive  oil  makers 
of  California.  One  was  a  so-called  "  pitter,"  the  other  a  "  crusher  "  or 
"  grinder."  These,  while  certainly  very  ingenious,  and  accomplishing 
the  object  in  view  under  certain  circumstances,  were  found  to  be  wholly 
unsuited  to  oil-making  in  California,  or  anywhere  else  where  economy 
is  an  object. 

It  is  generally  conceded  that  the  best  oil  is  made  from  the  first  pressing 
of  the  pulp  of  the  olive,  the  pits  being  unbroken.  Practically,  the  oil  of 
the  second  pressing  does  not  differ  materially  in  quality  from  the  first, 
always  provided  that  no  hot  water  is  used;  it  is  therefore  usually  mixed 
with  the  first  pressing.  This  is  especially  important  in  California,  where 
we  must  make  only  oil  of  the  very  finest  quality  if  we  would  hope  to 
compete  with  the  cotton-seed  oil  of  the  South  and  the  cheap  oils  of 
Europe;  it  being  generally  conceded  that  the  foreign  countries  can  make 
inferior  oil  far  cheaper  than  we  can. 

In  testing  these  machines,  then,  these  fundamental  points  must  be 
kept  in  view;  for  it  is  not  merely  by  the  ease  and  rapidity  of  their  work 
that  they  must  be  judged,  but  also  by  the  relative  quantity  of  oil  yielded 
from  the  first  and  second  pressings. 

The  Pitter  and  Crusher. 

The  so-called  "  pitter "  does  not  remove  the  pits  from  the  pulp,  but 
merely  tears  the  flesh,  without  breaking  the  pit.  This  is  rather  a  good 
point,  for  it  gives  stiffness  to  the  otherwise  slippery  mass.  The  machine 
itself  consists  of  an  endless  screw  in  a  metallic  sleeve.  The  olive  in 
passing  down  this  screw  is  forced  under  a  small  wheel,  which  partially 
crushes  it.  Should  the  olive  be  of  a  variety  having  a  large  pit,  the  latter 
will  be  broken.  If,  however,  the  olive  is  small,  it  will  pass  underneath 
the  crusher,  and  thus  give  little  or  no  oil  in  the  press.  Under  the  most 
favorable  circumstances,  the  yield  of  oil  from  this  is  far  below  that  of 
the  other  machines.  Hence,  the  Spanish  "  pitter  "  cannot  be  pronounced 
a  success  in  this  respect. 

The  second  machine,  the  "crusher,"  consists  of  two  iron  cylinders, 
ribbed,  and  turning  toward  each  other.  It  resembles  a  large  sausage 
grinder,  and  is  only  useful  in  grinding  up  the  dry  residue  from  the  first 
pressing,  preparatory  to  the  second  pressing.  While  it  certainly  does 
reduce  the  residue  to  a  finely  divided  state,  it  demands  so  much  motive 
power   that  a  good   power   engine   is   required.     Even  with   sufficient 


—   5   — 

power  it  allows  so  little  material  to  pass  through  at  a  time  that  it  falls 
far  short  of  the  efficacy  of  the  old  "  arrastra,"  or  rolling  millstones. 
Then,  too,  it  is  hard  to  clean,  requiring  the  work  of  a  good  man  for  ten 
hours  to  get  it  in  good  condition.  Besides  all  this,  it  is  of  untinned 
iron,  which  imparts  to  the  oil  an  "inky"  taste.  This  machine,  there- 
fore, proved  practically  a  failure  in  our  experiments. 

Failing,  then,  to  do  good  work  with  the  Spanish  machines,  and  hav- 
ing no  time  to  build  a  regular  "  arrastra,"  a  small  fruit-juice  press  was 
obtained.  This  consists  of  an  endless,  tapering  screw,  inclosed  in  a 
conical  sleeve.  The  olives,  entering  the  grooves  of  the  screw  at  the 
larger  end,  are  gradually  but  gently  mashed  and  twisted  till  the  flesh  is 
thoroughly  crushed,  without  the  pits  being  broken,  by  the  time  the 
olives  escape  at  the  smaller  end  of  the  machine.  Though  the  apparatus 
used  was  but  a  foot  long,  it  was  found  to  do  better  work  than  either  of 
the  other  two.  It  gave  more  oil  from  the  first  pressing,  and  while 
accomplishing  the  same  result  in  quicker  time,  was  easier  to  work.  No 
doubt  the  same  principle,  on  a  larger  scale,  would  give  excellent  results, 
and  be  cheaper  and  cleanlier  than  either  of  the  others. 

Oil  Presses. 

When  the  olives  have  been  crushed  they  form  a  mass  of  pulp,  pits, 
skins,  oil,  and  water.  In  order  to  press  the  oil  and  water  from  this,  it 
is  necessary  to  put  all  into  some  form  of  envelope,  porous  enough  to 
allow  the  liquid  part  to  escape  without  pulp,  pits,  or  skins.  In  Europe 
strong  circular  grass  mats  are  used.  These  are  filled  with  about  25 
pounds  of  pulp,  and  placed  one  upon  another  under  the  flat  "follower" 
that  is  attached  to  the  lower  end  of  the  screw.  When  it  is  practicable 
to  use  these  mats,  any  kind  of  oil  press  will  serve.  In  California  these 
mats  cost  from  $1  50  to  $2  apiece;  hence  are  too  expensive.  Cloth 
has  to  be  substituted  for  them,  but  the  use  of  cloth,  though  more 
economical,  necessitates  presses  specially  adapted  to  this  modification; 
for  when  the  pulp  has  been  divided  into  25-pound  packages,  and  wrapt 
in  cloth,  it  is  impossible  to  maintain  the  column  in  a  vertical  position, 
unless  some  kind  of  lateral  support  is  used.  This  is  done  by  the  use  of 
a  cylindrical  metallic,  perforated  sleeve  that  fits  closely  the  column  of 
pulp.  But  the  sleeve  cannot  be  used  unless  the  flat  steel  "follower"  at 
the  lower  end  of  the  screw  is  of  the  same  shape  as  the  sleeve.  Investi- 
gation has  shown  that  many  of  the  presses  on  the  market  are  adapted 
only  for  the  use  of  mats.  That  is,  the  flat  piece  of  steel  on  the  end  of 
the  screw  occupies  the  entire  space  between  the  iron  columns  that  sup- 
port the  screw,  and  there  is  no  room  for  the  sleeve.  The  press  in  use  at 
the  University  is  adapted  for  the  use  of  either  mats  or  cloth,  having  the 
"  follower  "  at  the  end  of  the  screw  circular,  and  smaller  than  the  sleeve. 
This  was  found  to  be  a  great  convenience,  and  economy  in  space,  labor, 
and  material. 

Cloth. — Finding  the  grass  mats  of  Europe  too  expensive  for  use  in 
California,  various  experiments  were  made  in  order  to  test  the  kind  of 
cloth  best  suited  to  the  conditions.  In  Southern  California,  and  else- 
where, "  Turkish  crash "  has  been  found  to  be  well  adapted  as  a  sub- 
stitute for  mats.  It  was  impossible  to  get  this  in  time,  so  various  grades 
of  coarse  "duck,"  linen  "  huck,"  and  sail-cloth  were  tried.  The  linen 
"huck"  was  an  unqualified  failure;   the  "duck"  was  better,  but  not 


—    6    — 

practical,  while  the  sail-cloth  worked  admirably.  The  cost  of  sail-cloth 
sufficient  to  envelop  twenty-five  pounds  of  pulp  is  about  50  cents.  The 
cost  of  a  mat  that  holds  the  same  quantity  is  from  $1  50  to  $2. 

The  "Separator" 

One  of  the  troublesome  processes  in  the  making  of  olive  oil  is  the 
separation  of  the  oil  from  the  watery  juice  after  it  comes  from  the  oil 
press.  The  universal  custom  is  to  collect  this  mixture  of  water  and  oil 
as  it  drips  from  the  press,  and  leave  it  several  hours;  then  to  skim 
off  the  oil  that  has  risen  to  the  top  by  reason  of  its  lightness.  This 
skimming  must  be  repeated  every  few  hours,  till  the  oil  is  entirely  sepa- 
rated; for,  if  not  at  once  removed  it  acquires  a  bad  taste,  from  the 
fermentable  juices,  which  are  heavily  charged  with  broken  tissues,  etc. 
Besides  the  necessary  hand  work,  it  requires  a  large  room,  and  a  very 
expensive  outfit  of  large  tanks.  In  order  to  avoid  all  this  expense  and 
trouble,  an  apparatus  was  made  that  performs  the  work  automatically 
and  continuously,  enabling  the  oil  maker  to  have  pure,  clean  oil  within 
two  minutes  from  the  time  it  leaves  the  press. 

Its  construction  and  working  was  seen  -  by  the  writer  in  the  oil-room 
of  Prof.  E.  Mingioli,  of  the  Royal  Agricultural  School  at  Portici,  near 
Naples,  Italy.  The  apparatus  as  shown  in  the  plate  consists  essentially 
of  a  tin  tank,  about  four  feet  high  by  two  in  diameter.  This  tank  is  kept 
constantly  full  of  fresh  water  by  means  of  a  pipe  connected  with  some 
adequate  supply,  the  level  being  regulated  by  means  of  stop-cock  outlets. 

The  juices  from  the  pressing,  charged  with  oil  in  a  finely  emulsified 
state,  are  made  to  flow  into  the  tank  near  the  bottom,  through  a  small 
"  drum,"  perforated  laterally.  Immediately  below  this  oil-escape  is  a 
larger  flat  "  drum,"  perforated  on  the  top,  from  which  a  stream  of  fresh 
water  escapes  in  vertical  jets.  These  two  currents  of  oil  and  fresh  water 
at  once  mix,  and  the  oil  passes  upwards,  by  reason  of  its  lightness. 
Being  in  very  small  drops,  it  is  washed  of  its  heavier  impurities  (tissue, 
coloring  matter,  etc.),  and  reaches  the  top  of  the  column  of  water  in  an 
almost  perfectly  clean  state,  having  left  all  grosser  impurities  to  be  car- 
ried off  through  an  escape  pipe  at  the  bottom.  When  sufficient  oil  has 
been  collected  at  the  top,  a  stop-cock  is  opened  and  the  oil  runs  off  ready 
to  be  clarified.  The  level  once  established,  the  apparatus  will  work 
uninterruptedly  for  a  long  time  without  being  cleaned  out.  Though  the 
small  quantities  of  olives  at  the  disposal  of  the  Station  did  not  permit 
of  any  long  continued  test  of  the  process,  yet  it  was  found  that  the  larger 
the  quantities  used,  the  better  the  separator  worked.  No  doubt  it  is 
susceptible  of  many  small  improvements,  such  as  automatic  regulators, 
etc.;  still,  on  the  whole,  it  was  found  to  work  very  well  indeed,  and  to 
be  a  vast  improvement  on  the  method  of  hand  skimming. 

A  model  of  this  "separator,"  together  with  oil  made  at  the  Station, 
and  olives,  olive  pits,  etc.,  can  now  be  seen  in  the  agricultural  alcove  of 
the  University  exhibit  at  the  Midwinter  Fair. 

CLARIFICATION    OF   THE    OIL. 

The  American  market  requires  that  olive  oil  should  be  put  in  glass, 
and  be  perfectly  clear  and  brilliant.  This  necessitates  careful  filtration. 
Strictly  speaking,  olive  oil  should  not  be  filtered  at  all,  for  by  the  pro- 


©Uve  Juice  orud 
oil    to   be  waihcd 


Cleat    0 


To*"  requlalnuj 
w«Ur    Uv*l 


Tor 


Cieanm 


Scale    I'.ljfc 


OLIVE  OIL  SEPARATOR. 
Designed  by  Prof.  Mingioli,  Italy. 


—   8   — 

cess  of  filtration  it  loses  a  great  deal  of  its  characteristic  taste  and  odor. 
Highly  clarified  oil  is  prettier  to  look  at,  but  is  not  as  agreeable  to  the 
taste  as  that  which  has  been  allowed  to  deposit  naturally  its  solid  mat- 
ter. The  oftener  an  oil  is  filtered,  the  more  neutral  in  taste  it  becomes. 
In  Europe,  oil  is  seldom  clarified  so  highly  as  in  America.  There,  sim- 
ple cotton-batting  is  used  for  oil  intended  for  domestic  purposes,  but  in 
California,  where  only  the  most  brilliant  oil  is  in  demand,  something 
less  porous  than  cotton-batting  is  required. 

In  the  oil-room  of  the  Station,  experiments  were  made  with  cotton- 
batting,  "glass  wool,"  asbestos,  and  filter-paper.  All  but  good  filter- 
paper,  such  as  is  used  in  chemical  laboratories,  was  found  to  be  unfit  for 
purposes  of  clarification.  Even  with  good  filter-paper,  some  varieties  of 
oil  were  found  to  require  two  nitrations  before  becoming  perfectly  clear 
and  brilliant.  It  was  also  noted  that  where  oil  was  at  once  filtered 
after  separation,  there  was  a  tendency  to  become  cloudy  after  a  month 
or  so  in  the  bottle.  Hence,  in  the  clarification  of  oil,  care  should  be 
taken  to  use  only  paper  of  such  good  quality  as  will  necessitate  but  one 
filtration. 

It  was  found  that  it  was  impossible  to  filter  olive  oil  in  a  room  where 
the  temperature  was  below  45°.  Of  course  no  heat  should  be  used,  but 
the  temperature  should  be  at  least  50°  F. 

The  absolute  avoidance  of  all  odors  in  the  oil-room  cannot  be  too 
stongly  insisted  upon. 

ANALYSES   OF    OLIVES   AND    OLIVE    OIL. 

The  twenty-four  analyses  made  in  the  laboratory  of  the  Central 
Station  during  the  two  previous  seasons  have  been  tabulated  with  those 
of  the  season  of  1893-94,  thus  giving  more  extended  data  for  compari- 
son of  the  value  of  varieties,  and  their  relative  adaptation  in  the  various 
parts  of  the  State. 

It  will  be  noted  that  the  tables  do  not  contain  the  iodine  absorptions 
as  in  previous  years;  also  that  a  column  showing  the  number  of  olives 
necessary  to  make  100  grams  has  been  added.  The  reason  for  this  inser- 
tion is  that  the  reader  may  be  enabled  to  form  a  pretty  accurate  idea  of 
the  relative  size  of  the  fruit  without  troublesome  cross  references.  This 
tabulation,  taken  with  Column  1,  which  shows  the  proportion  of  pits 
and  flesh  found  in  the  fresh  fruit,  enables  the  reader  to  determine  at  a 
glance  the  value  of  any  variety  for  pickling.  Take,  for  example,  Poly- 
morpha  and  Redding  Picholine.  In  one  case  it  takes  13  olives  to  make 
100  grams,  in  the  other  it  takes  an  average  of  79  olives.  Moreover,  in 
the  13  Polymorphas  there  is  17  per  cent  of  pit  and  83  of  flesh,  while  in 
the  79  Redding  Picholines  there  is  an  average  of  24.41  per  cent  of  pit 
and  75.58  of  flesh.  Keeping  in  mind  that  for  pickles  the  object  is  to 
have  an  olive  that,  while  being  as  large  as  possible,  has  the  smallest 
possible  pit,  one  has  little  trouble  in  judging  of  the  relative  merit  of 
whatever  varieties  he  may  have  in  mind. 

Column  2  shows  the  percentage  of  oil  it  is  possible  to  extract  from  the 
whole  fruit  by  the  most  careful  chemical  processes.  It  shows  also  the 
uselessness  of  taking  into  consideration  the  oil  contained  in  the  pits. 
Even  were  this  pit-oil  available  and  unobjectionable,  the  actual  quantity 
would  not   pay  for   the   trouble   of   extraction;    but   such   very  small 


—   9   — 

quantities  disseminated  throughout  a  mass  of  hard  material,  renders 
their  expression  by  mechanical  means  a  problem  of  no  practical  interest. 

But  aside  from  the  uselessness  of  attempting  to  extract  the  pit-oil,  the 
kernel  imparts  a  disagreeable  taste  to  the  oil  of  the  flesh  with  which  it 
comes  in  contact,  and  impairs  its  keeping  qualities. 

It  is  Column  3  that  serves  chiefly  for  the  study  of  the  values  of  olive 
varieties.  In  the  second  row  of  Column  1  we  find  the  percentage  of 
flesh  in  the  whole  fruit;  in  the  second  half  of  Column  3  we  find  what 
part  of  this  flesh  is  oil,  and  what  part  refuse  matter. 

Table  II  is  a  comparative  table  of  averages  of  those  varieties  of  which 
two  or  more  samples  were  received  at  the  Station.  It  is  to  be  regretted 
that  the  tables  are  so  incomplete;  but  it  was  too  late  in  the  season  to 
make  proper  arrangements  to  obtain  more  samples  when  the  work  was 
assigned  to  the  new  assistant. 

It  is  hoped  that  next  year  olive  growers  from  all  parts  of  the  State 
will  send  samples  of  the  varieties  they  may  have  to  the  Agricultural 
Experiment  Station  in  Berkeley,  in  order  that  this  study  may  be  made 
as  complete  as  possible.  It  is  only  with  the  cooperation  of  the  olive 
growers  that  the  problem  of  adaptation  of  varieties  to  soil  and  climate 
can  be  solved. 


—  10  — 


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Number  of  Samples 
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—  15  — 

Examination  of  Table  I  brings  out  the  importance  of  a  close  study  of 
soil,  climate,  and  varieties  before  undertaking  to  plant  an  olive  orchard. 
It  will  be  seen  that  there  are  varieties  that  yield  a  very  high  percentage 
of  oil,  and  others  that  do  not.  Further,  it  appears  that  the  same  variety, 
on  different  soils,  etc.,  will  vary  20  per  cent  in  the  amount  of  oil  yielded, 
while  the  crop  on  each  may,  to  all  appearances,  be  equally  heavy. 
Thus  the  Rubra,  in  one  place,  contains  as  much  as  34.90  per  cent  of  oil, 
and  in  another  locality  has  but  14.85  per  cent — a  difference  sufficient  to 
ruin  an  olive  grower  in  a  few  years.  This  variation  in  oil  yield  is 
most  easily  studied  in  Table  II,  in  which  the  maximum,  minimum,  and 
averages  have  been  conveniently  arranged. 

It  will  be  noticed  (Table  II)  that  in  the  eleven  varieties  of  which  more 
than  two  samples  were  received,  the  differences  between  the  maximum 
and  minimum  of  oil  in  fresh  fruit  varies  very  greatly:  thus,  while  in 
the  Rubra  the  difference  is  20.05,  in  the  Uvaria  it  is  only  4.20 — thus 
showing  for  the  latter  a  greater  uniformity  in  oil  percentages  for  the 
State  at  large.  The  following  list  comprises  the  commonest  varieties 
now  growing  in  California,  and  the  table  is  arranged  in  the  order 
of  highest  to  lowest  variations  between  maximum  and  minimum  oil 
percentage: 


Variety. 

Variation. 

Rubra 

20.05 

Oblonga                 -           

14.21 

Redding  Picholine 

13.10 

Nevadillo  Blanco  .     _ - 

13.06 

Mission __ 

11.09 

Pendulina 

10.00 

Prsecox 

7.45 

Atro-rubens _ 

6.50 

Manzanillo 

5.10 

Nigerina 

5.00 

Uvaria __. 

4.20 

The  table  shows  what  a  matter  of  "  guess  work "  the  selection  of 
varieties  for  orchards  in  the  State  has  been  thus  far,  and  emphasizes  the 
importance  of  the  work  undertaken  by  the  Agricultural  Experiment 
Station  in  bringing  out  all  of  these  various  characteristics. 

It  would  not  be  safe  to  pass  judgment  too  hastily,  taking  into  con- 
sideration the  relatively  small  number  of  analyses  at  our  command,  yet 
it  will  at  once  be  seen  that  there  are  varieties  that  seem  to  be  better 
adapted,  for  general  planting,  than  others.  Take,  for  example,  the 
Mission.  This  is  the  oldest  variety  cultivated  in  California,  and  we  have 
examined  thirteen  samples;  yet  it  stands  as  a  very  good  oil  variety,  never 
falling  below  19.20  per  cent  of  oil,  and  an  average  of  30  olives  in  100 
grams  (144  in  one  pound).  This  fact,  taken  with  the  experiments  in 
the  oil-room,  show  it  to  be  one  of  the  preeminently  safe  varieties  to  plant. 
It  gives  an  oil  of  very  good  quality,  and  one  that  keeps  its  marketable 
qualities  in  an  exceptionally  good  manner. 

What  is  said  of  the  Mission  can  be  said  of  the  Manzanillo,  which, 
while  being  a  trifle  larger  than  the  Mission,  is  a  more  regular  bearer,  and 
fully  as  hardy. 

The  Nevadillo  Blanco,  while  a  smaller  olive  than  either  of  the  other 
two,  is,  by  reason  of  its  high  average  in  oil,  and  its  regularity  as  a  bearer, 
one  of  the  olives  of  the  future. 


—  16  — 

The  Redding  Picholine  shows  itself  unworthy  of  the  place  it  has  in  the 
olive  plantations  of  the  State.  Though  it  is  a  good  bearer,  and  a  vigor- 
ous grower,  it  is  the  smallest  olive  of  any  of  the  varieties  thus  far  found  in 
California.  It  has  more  pit  and  less  flesh  than  any  other  variety.  Next 
to  the  Rubra  it  varies  more  than  any  other  in  the  above  table,  and  the 
oil- room  experiments  show  it  to  give  an  inferior  product.  Of  all  the  oils 
made  this  year  in  the  Station  oil-room,  that  of  the  Redding  Picholine 
was  the  "  greasiest "  and  the  first  to  solidify,  assuming  the  appearance  of 
partly  melted,  yellowish  lard. 

The  Uvaria  was  a  disappointment,  the  general  impression  being  that 
it  was  a  very  good  oil  variety,  so  far  as  regards  quantity. 

The  Rubra,  in  spite  of  its  uncertainty  as  to  richness  in  oil,  is  a  good 
variety  when  well  adapted  to  its  surroundings.  The  Rubra  oil  made  at 
the  Station  was  of  a  very  high  degree  of  excellence,  and  stood  cold 
weather  very  well. 

For  the  first  time  we  have  analyses  of  the  leading  Italian  varieties, 
i.  e.,  Grossajo,  Razzo,  Frantojo,  Correggiolo,  and  Morajolo.  From  the 
very  high  yield  of  oil,  when  we  take  into  account  that  the  Mission  on 
the  same  soil  gives  but  19.20  per  cent  of  oil,  we  are  led  to  conclude  that 
these  new  varieties  will  be  of  great  importance  in  the  future. 

Further  comment  is  not  deemed  wise  at  this  time,  owing  to  the  fact 
that  there  are  too  few  varieties  of  which  samples  were  received  from 
more  than  one  locality.  In  another  year,  with  the  cooperation  of  the 
olive  growers  of  the  State,  it  will  be  possible  to  discuss  more  fully  the 
results.  They  are  given  to  the  public  as  they  stand,  as  the  only  data 
existing  at  this  moment. 

The  thanks  of  the  Department  are  extended  to  Messrs.  Alfred  Wright 
and  J.  S.  Calkins,  of  Pomona,  J.  Rock,  of  Niles,  Hatch  &  Rock,  of  Biggs, 
and  Louis  Mel,  of  Livermore,  for  their  generous  donations  of  samples  of 
olives  in  lots  large  enough  to  be  made  up  into  oil. 


